Tube furnace

ABSTRACT

A tube furnace for the treatment of a continuously moving band of material which comprises a carbon or graphite furnace tube provided with radiation shields at each end of the hot zone thereof, which radiation shields comprise baffles of flexible carbon or graphite material, perforated to allow passage of the continuously moving band, and resiliently deformable in the direction of movement of that band. The furnace is particularly useful in the carbonization or graphitization of organic filamentary material.

United States Patent Higgins Feb. 8, 1972 [54] TUBE FURNACE [72] Inventor: Francis J. Higgins, Kenilworth, England [73] Assignee: Courtaulds Limited, London, England [22] Filed: Jan. 14, 1970 [21] Appl. No.: 2,692

[52] 0.5. CL ..l3/22, 13/25, 219/388, 219/390, 219/534, 219/552 [51] Int. Cl. ..H05b 3/66 [58] field ofSearch ..13/25,22,20,3l;219/388,

[56] References Cited UNITED STATES PATENTS 1,749,700 3/ 1930 Fourment ..219/155 1,916,810 7/1930 Schmidt 2,476,916 7/1949 Roscetal. ..13/31 2,778,866 1/1957 Sanz et a1 ..l3/20 2,906,627 9/1959 Payton et a1. l.219l388 UX 3,020,032 2/1962 Casey ..13/31 X 3,170,018 2/1965 .....13/31 3,345,448 10/1967 Malkin .....13/25 3,387,333 11/1968 Irvine et a1 ..219/528 Primary Examiner-Velodymyr Y. Mayewsky Attamey--Davis, Hoxie, Faithfull & l-lapgood [57] ABSTRACT A tube furnace for the treatment of a continuously moving band of material which comprises a carbon or graphite furnace tube provided with radiation shields at each end of the hot zone thereof, which radiation shields comprise baffles of flexible carbon or graphite material, perforated to allow passage of the continuously moving band, and resiliently deformable in the direction of movement of that band. The furnace is particularly useful in the carbonization or gaphitization of organic filamentary material.

7 Claims, 4 Drawing Figures msumm a me 3.641.249

Inventor FRANCIS JAMES HIGGINS DAVIS, 110x112, FATTHFULI. & HAPGOOD Attorne TUBE FURNACE This invention relates to an improved tube furnace and is particularly concerned with a tube furnace capable of operating at very high temperatures, for example at temperatures between 2,500" and 3,000 C.

In the continuous production of filamentary carbon, organic filamentary material is submitted to heat treatment under specific conditions of temperature, time, tension and surrounding atmosphere. Thus for example a tow of organic filaments, such as filaments consisting wholly or mainly of polyacrylonitrile, may be heated in a first stage to a temperature within the range from about 200 to 300 C. preferably in an oxidizing atmosphere and the product may be carbonized at a temperature of l,OO C. or more in an inert atmosphere. If it is desired to graphitize the resulting carbon filaments, a further heating stage is required in which the filaments are heated in an inert atmosphere to a temperature which is not less than 2,000 C. and is preferably not less than 2,500 C. The furnace of this invention is particularly suitable for employment in the graphitization of filamentary carbon, although it will be understood that the furnace may be adapted for other uses.

According to the invention a tube furnace for the treatment of a continuously moving band of material comprises a carbon or graphite furnace tube provided with radiation shields at each end of the hot zone thereof, which radiation shields comprise baffles of flexible carbon or graphite material, perforated to allow passage of the continuously moving band, and resiliently deformable in the direction of movement of that band.

In one form of the invention a cylindrical carbon tube comprises the heating element of the furnace which is heated by the passage of an electric current therethrough. At each end of the tube is provided a radiation baffle which consists of a disc of fabric made from fibrous carbon. Each baffle is perforated to allow passage of, for example, a tow of carbon filaments through the furnace tube and is retained in position within the tube by annular retaining means. The carbon fabric is flexible and is resiliently defonnable in at least one direction which is the direction of the passage of the tow of filaments or other moving body through the tube. Suitable carbon fabric includes woven material or preferably nonwoven carbon fabric such as carbon felt.

In a further form of the invention a similar carbon tube furnace is provided with radiation bafiles each of which comprises an annular bundle of staple carbon or graphite fiber deformable at least in the direction of movement of a tow of filaments through the tube and preferably having substantially all of the staple fibers aligned perpendicularly to that direction of movement.

The invention is based upon the observation that with a rigid radiation baffle difficulty can be experienced in, for example, the graphitization of carbon filaments in a continuous manner if an occasional filament breaks within the high-temperature zone. In due course a considerable number of broken filaments may bundle together and jam the tow in the outlet of the furnace. Similar difficulties may be met with on the inlet side. Using the arrangement of the present invention such difficulties are substantially obviated and an improved radiation shield efficiency may be obtained by suitable design of the baffles.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which FIG. 1 is a sectional elevation of one embodiment of a tube furnace in accordance with the invention,

FIG. 2 is a cross-sectional view taken on the line IIII of FIG. 1,

FIG. 3 is a sectional elevation of part of a second embodiment of a tube furnace in accordance with the invention, and

FIG. 4 is a cross-sectional view taken on the line IV-IV OF FIG. 3.

The furnace shown in FIGS] and 2 comprises a cylindrical furnace tube 1 of raphitized carbon having a hot zone section 2 WhICh is heated y the passage of an electric current through the tube. The tube 1 is surrounded by thermal insulation 3.

A tow 4 of filamentary material passes through apertures 5 and 5 in a pair of radiation shields 6 and 6', respectively. These shields are in the form of discs of carbon felt fabric and are resiliently deformable in the direction of movement of the tow of filaments, indicated by the arrow A. The interior of the furnace tube may be filled with inert gas retained by sealing means (not shown). The radiation shields 6 and 6 are supported within the tube on their downstream sides by retaining means 7 and 7 respectively. The radiation shields may also be supported by annular plates 8 and 8 on their upstream sides, so that the flexible material of the radiation shields is able to be deformed in the direction of movement of the tow, but is supported in the opposite direction.

In the furnace partly shown in FIGS. 3 and 4, the radiation shield is made from an annular bundle of staple carbon filaments 9 which is retained in the manner previously described by the annular support means 7 and 8. As will be seen from FIG. 3, the staple carbon fibers are substantially all arranged in the direction perpendicular to the direction of movement of the tow and thus are radially arranged in the bundle. As in the furnace of FIGS. 1 and 2, the radiation shields are resiliently deformable in the direction of movement of the tow.

Iclaim:

1. A tube furnace for the treatment of a continuously moving band of material, comprising a carbon or graphite furnace tube provided with radiation shields at each end of the hot zone thereof, which radiation shields comprise baffles of flexible carbon or graphite material perforated to allow passage of the continuously moving band, and resiliently deformable in the direction of movement of that band, means for mounting said shields in said furnace, and means for heating said tube.

2. A furnace as claimed in claim 1 in which the tube is cylindrical.

3. A furnace as claimed in claim I in which the tube is heated by the passage of an electric current therethrough.

4. The furnace as claimed in claim 1 in which the baffles are perforated discs of fabric made from fibrous carbon or graphite.

5. A furnace as claimed in claim 4 in which the baffles are made from nonwoven carbon fabric.

6. A furnace as claimed in claim 1 in which each of the baffles is formed from an annular bundle of staple carbon or graphite fiber.

7. A furnace as claimed in claim 6 in which in the bundles of staple carbon or graphite fiber substantially all the staple fibers are aligned perpendicularly to the direction of movement of the material through the furnace. 

1. A tube furnace for the treatment of a continuously moving band of material, comprising a carbon or graphite furnace tube provided with radiation shields at each end of the hot zone thereof, which radiation shields comprise baffles of flexible carbon or graphite material perforated to allow passage of the continuously moving band, and resiliently deformable in the direction of movement of that band, means for mounting said shields in said furnace, and means for heating said tube.
 2. A furnace as claimed in claim 1 in which the tube is cylindrical.
 3. A furnace as claimed in claim 1 in which the tube is heated by the passage of an electric current therethrough.
 4. The furnace as claimed in claim 1 in which the baffles are perforated discs of fabric made from fibrous carbon or graphite.
 5. A furnace as claimed in claim 4 in which the baffles are made from nonwoven carbon fabric.
 6. A furnace as claimed in claim 1 in which each of the baffles is formed from an annular bundle of staple carbon or graphite fiber.
 7. A furnace as claimed in claim 6 in which in the bundles of staple carbon or graphite fiber substantially all the staple fibers are aligned perpendicularly to the direction of movement of the material through the furnace. 